package com.huwaiwai.aqs;

import java.io.Serializable;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * Created by hww on 2018/6/3 上午10:16.
 */
public class Mutex implements Lock, Serializable {

    private static final long serialVersionUID = 5784678340839593641L;

    private static class Sync extends AbstractQueuedSynchronizer {

        boolean isAlive() {
            return getState() == 1;
        }

        public boolean tryAcquire(int acquires) {
            assert acquires == 1;
            if (compareAndSetState(0, 1)) {
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        protected boolean tryRelease(int releases) {
            assert releases == 1;
            if (getState() == 0) throw new IllegalMonitorStateException();
            setExclusiveOwnerThread(null);
            setState(0);
            return true;
        }

        Condition newCondition() {
            return new ConditionObject();
        }
    }

    private final Sync sync = new Sync();


    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1, unit.toNanos(time));
    }

    @Override
    public void unlock() {
        sync.tryRelease(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }

    public boolean isLocked() { return sync.isAlive(); }
    public boolean hasQueuedThreads() { return sync.hasQueuedThreads(); }

}
